Implantable medical devices can include cardiac function management (CFM) devices such as implantable pacemakers, implantable cardioverter defibrillators (ICDs), cardiac resynchronization therapy devices (CRTs), and devices that include a combination of such capabilities. The devices can be used to treat patients or subjects using electrical or other therapy, or to aid a physician or caregiver in patient diagnosis through internal monitoring of a patient's condition. The devices may include one or more electrodes in communication with one or more sense amplifiers to monitor electrical heart activity within a patient, and often include one or more sensors to monitor one or more other internal patient parameters.
Implantable medical devices typically include one or more implantable leads that can be positioned to contact the endocardium within one or more heart chambers or positioned to contact the epicardium. The leads include one or more electrodes to deliver electrical stimulation therapy or to sense intrinsic cardiac activity. The leads can be a source of potential device malfunction due to mechanical or electrical failure. An implantable device also typically includes electronics unit within a hermetically sealed housing. The electromechanical interface between the leads and the electronics unit can also be a source of potential device malfunction.
A leadless approach for endocardial pacing can address some of the challenges associated with implantable leads. However, this approach includes conflicting requirements to minimize electrode area for stimulation yet maximize electrode area for sensing. The present inventors have recognized a need for improved electrode design in leadless pacemakers.